Projection lamp



PROJECTION LAMP Filed Dec. 9, 1957 INVENTORS Ma S .0

N am w. FA M ATTORNEY PROJECTION LAMP Sandford C. Peek, Jr., Hamilton,Mass, and Jan A. Van Den Brock, Ann Arbor, Mich., assignors, by mesneassignments, to Sylvauia Electric Products Inc., Wilmington, Del., acorporation of Delaware Filed Dec. 9, 1957, Ser. No. 701,414 9 Claims.(Cl. 313-113) This invention relates to electric incandescent lamps andespecially to lamps designed for use in moving picture projectiondevices or in other devices requiring a high concentration of lightenergy on a limited area.

Such lamps have been made heretofore for use with an external reflector,or with a metallic reflector deposited on the inside of the glass bulbof the lamp. When an external reflector was used, it had to be madelarge compared with the dimensions of the lamp, in order to reflect asuflicient amount of the light in'the desired direction. Thisnecessitated a large enclosure for the project ing system, withconsequent cumbersomeness and expense. In addition, there was thedifliculty of properly aligning the lamp filament with the reflector,since the lamp has to be made detachable for replacement purposes.

2,979,634 Patented Apr. 11, 19 61 during life much better than do lampswith a reflector coating deposited on the lamp bulb.

When a lamp according to the invention is used in a moving pictureprojector, the condenser lens or lenses ordinarily used in suchapparatus becomes unnecessary, and the film gate can be positioned sothat it will be filled with an image of the filament, the image beingenough out of focus to be fairly uniform in intensity over the area ofthe gate. The solid angle of the reflector need only be great enough sothat the light rays passing through the film gate will be at the properangle to fill the objective lens used on the other side of the gate, forfocussing the picture on a screen.

The increase in etficiency of useful light output is so great that, in apropector for 8 mm. film, a 50-watt filament in a lamp of our inventioncan be as effective as a 500-watt filament with an external reflector,thus greatly reducing the amount of heat to be dissipated in theprojector or other devices in which the lamp is used. However, becauseof manufacturing tolerances, voltage requirements and the like, aISO-watt filament will gen- Eliminating the external reflector and usinga reflecting surface deposited on the interior or exterior surface ofthe lamp bulb provided a more compact unit, but introduced theadditional difficulty of forming the glass bulb to a special and veryprecise shape. The shape could not be controlled precisely enough withthe usual methods available for molding glass bulbs. Furthermore, thereflector was on the lamp bulb and the filament was on the lamp mount,so the proper positioning of filament and reflector was diflicult tocontrol accurately when the flare of the mount was sealed to the openend of the bulb. The alignment had to be fixed with precision while theseal was still hot and plastic, and before it solidified. A base thenhad .to be aflixed to the lamp and aligned.

We have found that the above difliculties can be avoided by making thelamp with an internal reflector, separate from the bulb, and supportedsolely from the same mount which supports the filament. The reflectorand filament can then be aligned directly on the mount before the latteris sealed to the bulb. The filiment can be supported on wires fixed tothe reflector support, and the two lined up approximately with eachother before they are even attached as a unit to the mount. If the mountis made on a flat glass disc, or header, with rigid lead-in wiresextending therefrom to act as contacts for engagement with a suitablesocket, the difliculties of aligning the filament and reflector with asubsequentlyattached base, are also eliminated.

Moreover, the filament can be made in a concentrated coil; and thereflector placed very close to the coil, so that a very small reflectorwill suflice.

With the reflector close to the filament, however, a small change inposition of the filament will greatly affect the focusing of the bulb;accordingly, the filament should be one which will not be appreciablydeformed on heating to its operating temperature. The filament mustremain in a substantially fixed position. Such a filament coil can bemade in the manner shown in United States patent application Serial No.674,364, filed July 26, 1957 by Wilfrid G. Matheson.

"The lamps of our invention maintain their lightoutput e'rally be used.

Other objects, features and advantages of the invention will be apparentfrom the following specification, taken in conjunction with the attacheddrawings in which:

Fig. l is a front view of one embodiment of the invention;

Fig. 2 is a side view, partly in section, of the same device; and l Fig.3 is a back view of the device.

In Fig. 1, a front view of the finished lamp, the tubular glass bulb 1encloses a reflecting surface 2 and a tungsten filament 3 at or near thefocus of the reflecting surface.

The manner in which the reflecting surface 2 and filament 3 aresupported, is shown in more detail in Figs. 2 and 3. In Fig.2, the bulb1 has a disc-like glass header 4 sealed to its neck 5, the latter beingof smaller diameter than the main portion 6 of bulb 1. The other end 7of the bulb is rounded as shown, and preferably covered by the coating8, which can be of a colored or black enamel glaze suitable for scalingto the glass of the bulb. This coating increases the heat radiation fromthe top of the bulb so that it operates at a lower temperature. j

In order to provide supports an external contacts, leadin wires 9, 10,11, 12 are sealed through nubs 13, 14, 15, 16 in the header 4, a metalcapable of scaling to the glass nubs being used. Such metals arewell-known in the art. For example, if the bulb 1 is of the soda-limeglass often used in lamps, the lead-in wires 9-12 can be of so-calledcopper-weld wires, which are of stiff steel with a thin copper sheath.

' fIhe reflecting surface 2 is of metal, for example, silver oraluminum, deposited on the concave surface of the glass piece 17 bymethods well-known in the art, forexample, deposition by evaporation andcondensation in a vacuum. The glass piece 17 has nubs 18, 19, 20, 21 onits convex back surface 22. A short wire 23, 24, 25, 26 extends out ofeach nub, and is sealed therein, the wires 23-26 extending only part wayinto the glass in order to be insulated from the metal reflectingsurface 2 and to avoid damaging the latter. I

The reflecting surface 2 can, of course, be present on an all-metalpiece, if desired, in which case glass beads could be inserted in thelead-in wires to prevent shortcircuit of the filament by the metallicreflecting piece to which the lead-in wires would be mechanicallyconnected; A copper-piece, plated with silver can be used asthereflector.

Support wires 27, 28, 29, 30 are welded to the wires 23, 24, 25, 26 oneof the latter wires to each support wire. The longer supportwires 29,30., extend downwardlyand toward each other, being curved slightly toconform to the curvature of glass piece 17, and are welded at theirbottom ends to a metal cross-wire 31, which extends between the lead-inwires 11, 12, being welded to each of them. This gives a firm supportfor the top end of the glass piece 17.

Each of the wires-23, 24, extending from nubs '18, '19, is affixed toone, and one only, of the supportwires 27, 28, which curve downwardlyaround the convex back 22 of glass piece 17 to the lead-in wires 9, 10,each being welded to one and one only of said lead-in wires. As a resultof this and the additional supporting wires 27, 28, the glass piece 17is supported very rigidly from the header 4.

The filament 3 isa coiled-coil of tungsten wire, of a non-sagconstruction formed as in copending U.S. patent application Serial No.674,364, filed July 26, 1957, by W. G. Matheson, and assigned to thesame assignee as the present application.

In order to support and make electrical connections to the filament 3,metal support wires 33, 34, are clamped or Welded to the ends thereof,one end to each wire, and the wires are spaced apart by the transversespacing wires 36, 37, which are sealed to insulating glass bead 33,their ends being spaced apart in the bead to prevent shortcircuiting ofthe filament. The support wires 33, 34 are curved to form bights attheir bottom ends 39, 40 and welded near those ends to, respectively,the support wires 27, 28, which in turn, are welded to the lead-in wires10.

In that manner, the filament 3 and the metallic reflecting surface 2 areheld in perfect alignment with each other independently of the alignmentbetween header 4 and bulb 1, and, of course, without the need ofsubsequent alignment with an external reflector. However, due to thecloseness of the filament to the reflecting surface, even a smallvariation in filament position can affect the amount of light reflectedto a given spot and so the filament must be formed in a manner whichprevents sagging when the filament is heated. A method of so forming afilament is shown in the Matheson application above mentioned.

The filament and reflector can be aligned on the mount by means of jigs,if desired, and the jigs afterward removed.

A metal base shell 43 is attached to the neck 5 of the bulb 1 by thecement 44, and carries the outwardly projecting piece 45, which coversand protects the sealed exhaust tube 46 and, together with the keyway47, also serves to center the lamp in its socket, the base and socketbeing shown in copending US. application Serial No. a

553,367, filed December 15, 1955, by William Morgan. The glass nubs 13,15, and the like, pass through holes in the bottom of the shell 43, asshown in Fig. 2, so that the lead-in contact wires 9, ll), 11, 12 areinsulated from said shell.

: The rounded protuberances 48, which may be three in number, extendradially outward from the base shell 43, to help position the lamp inits socket, as shown in said copending application of William Morgan.

For best results, the reflector should be highlypolished no to give asmooth surface. An elliptical surface can be used, with the filamentoffset from the focus enough to give fairly uniform illumination at thefilm gate. A sharp image of the filament would be undesirable.

Very good results have been obtained with a spherical f No condensinglens is necessary with the device of our invention.

In order to give good eificiency and life, the lamp is filled with a gasinert with respect to the filament, preferably at a pressure aboveatmospheric. A filling of nitrogen at a pressure of about 1000millimeters of mercury is satisfactory. The exhaust tube 4 can be sealedat a pressure above atmospheric by methods now wellknown in the art, forexample as shown in copending U.S. patent application Serial No.594,305, filed June 27, 1956, now Patent No. 2.837,880, by AlexanderRosenblatt et al., assigned to the some assignee as the presentapplication.

In a lamp having a reflecting surface deposited on the inside of theglass bulb, the metallic vapors from the filament tend to deposit on thereflector, blackening it and reducing its reflective power. When thereflector is spaced from the bulb, however, the convection, currentswill carry the vapors upward and away from the reflector, so that theywill eventually deposit on the glass bulb. A considerable part of thevapor will deposit on the part of the bulb behind the reflector Where itdoes not reduce the light output.

Various modifications of the device described can be made by a personskilled in the art without departing from the spirit and scope of theinvention.

What we claim is:

1. An electric incandescent lamp comprising a sealed bulb oflight-transmitting material, two lead-in wires sealed therethrough, aconcentrated coiled filament inside said bulb and connected to saidlead-in wires, and a curved metallic reflector inside said bulb andspaced therefrom and having its axis perpendicular to the axis of thebulb, said reflector being in position to reflect light from saidfilament, said metallic reflector being supported at least partly fromsaid lead-in wires but insulated therefrom.

2. An electric incandescent lamp comprising a sealed bulb oflight-transmitting material, said bulb being closed by a substantiallyflat portion, a reflector inside said bulb and of different curvaturethan said bulb and having its axis perpendicular to that of said bulb,and'a concentrated coiled filament inside said bulb and in reflectingrelationship with said reflector, rigid lead-in wires extending throughsaid substantially flat portion of said bulb to act as'external contactprongs, said reflector being supported from some of said lead-in wires,said filament being supported from some of said lead-in wires on thesame substantially flat portion of said bulb as said reflector tomaintain the filament and reflector in alignment.

'3. An electric lamp comprising a sealed tubular bulb of lighttransmitting material, one end of said bulb being closed by asubstantially flat header, at least three lead-in wires extendingthrough said header, a curved reflector supported from all of saidlead-in wires, and a concen trated coiled filament supported by wiresconnected to two only of said lead-in wires but insulated from saidreflector, said reflector being in position to reflect light from saidfilament in a direction substantially perpendie ular to the axis of thebulb.

'4. The lamp of claim 2, in which the reflector is a curved rigid glasspiece having a reflecting coating on the sidethereof nearest thefilament.

5. The lamp of claim 4, in which the reflector is sup ported by wiressealed into the side of the glass piece farthest from the filament, theWires extending part way only into the glass to be out of contact withthe reflecting metal coating. 7

6. An electric lamp comprising a sealed tubular envelope oflight-transmitting material, one end of said bulb being closedbyaheader, straight, rigid lead-in wiresextending through said header, acurved glass piece in said bulb with its axis perpendicular to the axisof said bulb, said glass piece having aconvex and aconcaye side, withfour nubs projecting from its convex side, sup

porting wires sealed into said nubs but extending only partly throughthe glass piece, a reflecting metal coating on the concave side of saidglass piece, a concentrated coiled electrically-conducting filament atthe focus of 'said reflecting coating, each end of said filament beingconnected to an electrically-conducting support wire connected to one ofthe supporting wires for said glass piece, the supporting wires for saidglass piece being connected to the rigid lead-in wires inside said bulb.

7. An electric incandescent lamp comprising a sealed envelope having alight-transmitting portion, a curved reflector in said bulb with itsaxis perpendicular to that of said bulb, rigid support wires for saidreflector, a

concentrated coiled filament, electrically-conducting wires mechanicallyconnected to and extending from said support wires to position saidfilament in reflecting relationship with said reflector.

8. An electric incandescent lamp comprising a sealed envelope having alight-transmitting portion, a spherical reflecting surface in said bulb,to direct light through said light-transmitting portion, and aconcentrated coiled filament in said bulb at a point about halfwaybetween the surface of said reflector and the center of curvaturethereof in a direction substantially perpendicular to the axis of thebulb.

9. An electric incandescent lamp comprising a tubular bulb, having acolored end, a header sealed to the opposite end of said bulb andclosing the same, lead-in wires sealed through said header, aconcentrated coiled filament in said bulb and connected to said lead-inwires, and a concave metallic reflecting surface within said bulb and ofdifferent curvature than said bulb and having its axis perpendicular tothat of said bulb, said metallic reflecting surface being supported fromsaid lead-in wires but insulated from said filament in position toreflect light out of the clear tubular walls of the bulb and away fromthe 299,885 Welsh June 3, 1884 654,208 Washbnrn July 24, 1900 1,344,429Ricker June 22, 1920 1,635,116 Du Breuil July 5, 1927 1,800,926 BairdApr. 14, 1931 1,835,705 Gilleland et al Dec. 8, 1931 1,863,547 ArbuckleJune 14, 1932 1,936,854 Parker Nov. 28, 1933 1,998,967 Reynolds Apr. 23,1935 2,144,438 Birdseye Jan. 17, 1939 2,795,722 Burgener et a1 June 1'1,1957

